Hearing impaired individuals who attend conference-type meetings generally have difficulty hearing everyone at the table. Even people with only moderately impaired hearing, and who do not wear hearing aids, are often in need of amplification.
Sound reinforcement, if available, requires setting up microphones and cables, often creating an uncomfortable meeting environment. The arrangement is rarely effective for the hearing impaired person and may even create adverse acoustics for the normal hearing participants.
People who wear hearing aids also have a difficult time hearing, even though they have personal amplification. This is because of the placement of the hearing aid which most people wear behind the ear. In a conference situation, the micropone of the hearing aid is behind the listener and facing away from the table. Since the microphone is not in the direct path of the sound waves produced by the meeting participants it picks them up after they have been reflected off another surface such as a wall. These reflected waves, arriving at different times, are out of phase causing distortion.
Another problem is that meeting participants are at varying distances from the hearing aid microphone. Those individuals that are closer to the hearing aid will sound louder than those that are further away.
Still another problem caused by hearing aids is that environmental noise is amplified at the same rate as the desired signal. The result is a low signal to noise ratio where noise and distortion are almost indistinguishable from the sound the listener wishes to hear.
To overcome these problems, the hearing aid microphone would ideally have to be located in the center of the table directly in the path of the sound waves crossing the table and equidistant from all speakers. Additionally, the microphone should be designed to favor the desired sound waves while reducing those that are undesirable. The simplest way to accomplish this objective is to establish directional characteristics for the microphone that are optimally effective for this type of acoustic environment.
Finally, the microphone needs to be capable of wireless operation so that people can move freely about the conference table without the presence of annoying wires. Such a device would also be useful for sound reinforcement and recording providing performance that is superior to conventional microphones, as well as the convenience of wireless operation.
The prior art includes U.S. Pat. No. 4,361,736 to Long which describes a pressure responsive acoustical insulated microphone diaphragm closely spaced to a boundary and adapted to receive sound waves only through that space in order to provide realistic multi-directional sound reproduction with the ability to acoustically filter and cancel unwanted signals in the higher frequency range. Although the Long patent does mention a microphone closely spaced to a boundary that is parallel to the table top; it does not disclose a cone suspended above and perpendicular to such boundary which produces a higher electrical output of voice frequencies and specific directional characteristics for a conference environment, or a structurally integrated antenna system for wireless operation.
Also of interest are U.S. Pat. No. 2,544,536 to A. H. Kettler pertaining to a micropnone and U.S. Pat. No. 2,577,288 to E. H. Terlinde on an acordian microphone. It should be pointed out that the cone in the applicants' invention has an entirely different function from the cone-shaped portion of the Terlinde patent. In the latter patent there are several openings for the sound to enter, whereas applicants' cone functions as a vertical boundary by providing only one opening through which the sound may pass.
U.S. Pat. Nos. 3,496,297 to R. Brumberger and 2,267,353 to G. Lahovsky are considered to be of marginal interest. Finally, U.S. Pat. No. 3,870,820 to Suzuki et al discloses a built-in microphone for a tape recorder. None of the foregoing patents is believed relevant enough to affect the patentability of the present invention which is clearly an improvement over the prior art since it is uniquely suited to meet the objectives of a wireless conference microphone.